Nema 23 stepper motor run slowly and stuck at high speed

MaxHeadRoom

Joined Jul 18, 2013
22,346
Yes Max, modern PWM systems can do a lot of wonderful things. But the math is more complex to explain than the RL time constant approach. You are totally welcome to derive the explanation for the PWM method for us all to see.
See the Gecko web site for explanation, my point was that the resistor drop method has not been used for some time now.:rolleyes:
Max.
 

atferrari

Joined Jan 6, 2004
4,197
The switching from +HV(40) to +LV(8) happens shortly after the phase sees the +HV to turn it on. The di/dt is reduced in magnitude and there is no kickback here because the +LV supply has way more current capacity than the +HV supply. The kickback occurs when the phase is turned off. It has a magnitude of perhaps +80V or so that is used to charge a capacitor whose other side is connected to the +HV supply, helping to hold it up.

Better than a timing diagram I might be able to make a schematic from the hand drawing: would that be helpful?
Sure @Papabravo and I will appreciate that.
 

Papabravo

Joined Feb 24, 2006
15,068
Sure @Papabravo and I will appreciate that.
It took me a while to find the schematic. It was in with the photo masks we used to fabricate the board. I have excerpted the schematic to show the power supply switching and the flyback catcher. The file won't simulate because I don't have any models for the parts we used, and I had to add comments for the actual parts. Also note the the TIP645 is actually a darlington but I couldn't quickly find a symbol for it.
Enjoy
 

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